Wednesday May 08, 2024
Kenya- Burundi- Brazil- Dubai- Somalia- China
By Nick Perry
In Kenya, China, Dubai, Brazil and Somalia, devastating floods have hit hundreds of thousands of people.
While not all are directly linked to global warming, they are occurring in the midst of record-breaking heat waves, illustrating the warning from scientists that climate change is increasing the frequency and intensity of extreme weather events.
Because climate change is not just about rising temperatures, it also involves a whole range of effects linked to excess heat stored in the atmosphere and oceans, due to mankind’s release of greenhouse gases, including carbon dioxide (CO2).
“Recent extreme precipitation events are in line with what is expected in an increasingly hot climate,” Sonia Seneviratne, a member of the IPCC, the UN-mandated group of climate experts, told AFP.
Warmer oceans evaporate more, and warmer air can hold more water: for one degree more, the atmosphere can hold 7% more moisture.
“This leads to more intense rainfall episodes”, noted Davide Faranda, a specialist in extreme weather phenomena at the CNRS.
In Pakistan in April, it rained at least twice as much as the average, with one province recording 437% more. In Dubai, the rainfall of two normal years fell in just one day.
– Thirsty atmosphere –
But not all regions of the globe are getting wetter.
“A warmer, thirstier atmosphere is more effective at absorbing moisture from one region and redistributing this excess moisture in the form of storms elsewhere”, according to Richard Allan, from the University of Reading, England.
This leads to more rain in some places, but also more intense drought and heatwaves in others, he explains .
Natural climatic variations also influence rainfall. This is the case of the natural cyclical El Niรฑo phenomenon over the Pacific, known for its warming effect, which has been fuelling record global temperatures for almost a year now, but also extreme rainfall in certain countries, including Peru and Ecuador.
However, despite natural variations, “the observed long-term increase in heavy rainfall is due to human-induced climate change”, stresses Ms Seneviratne.
– Unsuitability –
Not all floods are attributable to climate change, whose influence on each event must be examined on a case-by-case basis.
However, scientists now have methods for quickly comparing a current episode of extreme rainfall, heatwave or drought with the probability of it occurring in a world without climate change.
Pioneers of this approach, the World Weather Attribution (WWA) network concluded that the torrential rains in the United Arab Emirates and Oman in April were “very likely” exacerbated by global warming, mainly caused by the burning of fossil fuels.
ClimaMeter, which uses a different methodology, believes that the April floods in China were “probably influenced” by the conjunction of climate change and El Niรฑo.
“It can be difficult to distinguish global warming from natural fluctuations” and this is more obvious for some weather events than others, says Flavio Pons, a climatologist who studied the Chinese floods.
For the floods in Brazil, ClimaMeter believes that climate change is primarily responsible for the intensification of rainfall, with no significant influence from El Niรฑo.
“It can be difficult to distinguish global warming from natural fluctuations” and this is more obvious for some weather events than for others, says Flavio Pons, a climatologist who has studied the Chinese floods.
For the floods in Brazil, ClimaMeter believes that climate change is primarily responsible for the intensification of rainfall, with no significant influence from El Niรฑo.
Many of the countries most affected by flooding, such as Burundi, Afghanistan and Somalia, are among the poorest and least equipped to cope with heavy rains.
But the Dubai episode showed that wealthy countries were not sufficiently prepared either.
“We know that a warmer climate favors extreme metrological events, but we can’t predict exactly when and where this will happen,” stressed Joel Hirschi of the UK’s National Oceanography Centre.
“Current preparations are insufficient”, he stressed, while it is “cheaper to invest today” than to wait.
Humaniterre with AFP
